This invention has application in several fields, as discussed below. However, since it is particularly suitable for waste disposal and hazardous waste landfill it will be described in detail with particular reference to landfill applications.
All states require a daily cover over trash being placed in a sanitary landfill. This is accomplished by the application of cover material, usually soil, at the end of each day. The general requirement for this daily cover is six inches of soil, although thinner sections of alternate covers can be used. In some states the regulations even require alternate covers to be six inches thick.
In the past, soil has been used in most instances as a cover material. It can readily be appreciated that certain disadvantages attend the use of soil as a daily waste cover. In the first place, when soil is used, there is a continuing need to have sufficient soil available to meet the requirements of daily cover. Secondly, and more importantly, the use of soil layers at the above-noted thicknesses results in the rapid depletion of disposal space in the landfill. Most states permit the use of a foam material for a daily cover in landfill operations in place of soil, provided that the foam material meets certain requirements, e.g., it must be effective to seal off odors from, and prevent insects from gaining access to, the waste. Furthermore, it must be inoccuous to the environment.
Recently, surfactant-based foams have been developed for daily cover of waste and landfill operations. These foams have the advantage over soil cover that they will collapse when additional waste is deposited on top of the foam, therefore they do not consume valuable landfill volume. Currently available foams, however, are not suitable for use as landfill cover when the slope of the landfill surface is greater than about 30 degrees and the section thickness is greater than 3 to 4 inches. These foams tend to "cold flow" down the slope at these conditions.
The two-part hardening foams described in U.S. Pat. Nos. 2,945,322 and 4,519,338 do not satisfy the above conditions since they can not be deposited at the required six inch thickness.
The increasingly stringent requirements of state and Federal environmental agencies and the growing shortage of useable waste disposal landfill volume, have given impetus to a continuing search for materials that meet the above criteria for suitable daily waste landfill cover without having the above-noted disadvantages